This invention is related to apparatus for generating seismic waves for locating sub-surface structure, and more particularly to mobile apparatus for generating a P wave and then a shear wave without the necessity of relocating the vehicle on which the wave-generating apparatus is mounted.
Apparatus is known for generating either P waves or shear waves in the earth to provide information regarding sub-surface structure. Generally a P wave is produced by a weighted hammer striking the horizontal surface of an anvil embedded in the earth. Shear waves are produced by the hammer striking a vertical impact surface.
One method for generating such a wave is to mount a hammer connected to a weight of about a thousand pounds on an upright boom. The hammer is then dropped so that it strikes an anvil resting on the ground. The boom is supported on a vehicle which must be repositioned to produce a shear wave in the same location as the P wave.